Method for burning oils



United States Patent Ofiiice 2,894,823 Patented July 14, 1959 METHOD FOR BURNING OILS Ralph W. Chapin, Long Beach, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application March 26, 1956, Serial No. 573,672 4 Claims. (Cl. 23-230) This invention relates to a method for burning oils and particularly relates to a method for laboratory burning of oils for ash determinations in which smoking and soot formation have been eliminated.

In the laboratory analysis of liquid fuels, particularly fuels heavier than gasoline and boiling above about 400 F., the noncombustible materials are determined as ash by igniting the oil and allowing it to burn to leave a heavy semi-liquid or solid coke-like residue. This material is then heated to temperatures of about 800 F. to drive off any remaining volatile matter and loosen the ash from the dish. The ash is then calcined in platinum at 1000 F. This analysis is very important with respect to burner oils wherein excessive amounts of ash will interfere with burner performance and may even cause slag deposition on heat transfer surfaces if the ash is excessively high. The analysis is also of critical significance in determining the quality of hydrocarbon feedstocks fed to catalytic cracking processes and other processes in which the oil is contacted with granular solid contact materials. The nonvolatile and noncombustible materials, particularly metallic elements and their compounds, can have a very detrimental effect on catalyst activity. For these reasons routine ash analysis of the heavier hydrocarbon oils is made.

The customary procedure for determining ash content involves the uncontrolled burning of the sample. In such burning the sample is unheated except by heat transfer from its own flame, a free supply of atmospheric air is available, and the oil burns as fast as vaporization can take place. In nearly all cases such burning liberates excessive smoke, and soot formation occurs. Aside from the atmospheric pollution effects, the amorphous hydrocarbonaceous material in the soot and smoke discharged by such burning has been found to contain much unburned and unvaporized oil carrying with it its noncombustible, nonvolatile residue or ash. This material is thus lost from the sample and renders the ash determination low. It thus indicates a higher grade oil than actually was burned.

The present invention is therefore directed to an improved laboratory method for oil sample burning in which smokeless controlled burning of the oil sample is efit'ected without the loss of unburned oil and which therefore does not cause atmospheric pollution.

It is a more specific object to provide a method for the ashing of relatively heavy liquid fuels to avoid the formation of smoke and soot and the loss of part of the sample therewith.

Other objects and advantages of this invention will become apparent to those skilled in this particular art as the description and illustration thereof proceed.

The present invention comprises a method in which a liquid oil sample dish is supported above a bench on a screen or grid or other relatively rigid support through which air can flow. This is essential as the apparatus will not perform effectively without such air flow. A metal chimney, preferably cylindrical, is supported coaxially above the dish and provided with suitable adjustments so that its elevation relative to the dish may be changed. The chimney is further provided with a plurality of lateral openings disposed in a row around its periphery just above its lower end. Within the burner and just below the lateral openings is disposed a ring manifold having a plurality of openings for gas flow on the inner surface. A valved inlet opens through the chimney wall into the manifold and gas supplied thereto is projected radially inward and burned within the chimney above the sample dish.

The chimney height and the gas rate to the manifold are adjusted to obtain smokeless burning and the relative adjustment of these two variables depends on the nature of the oil and the degree to which the original oil sample has been burned. The rate of burning of the sample in the apparatus of this invention is controlled at all times and is somewhat slower than open uncontrolled burning. There is no formation of wet soot or smoke and accordingly no hydrocarbon losses, thus closely reproducible ash determinations of high accuracy are obtained.

To use the apparatus the sample dish containing the sample is placed upon the support grid and the chimney moved down over the dish in a position so that its lower edge is about even with or slightly below the top edge of the sample dish. The oil sample is ignited and for a very short period smoke appears at the top of the chimney. Fuel gas is immediately turned into the manifold and increased in rate until no smoke is visible. The height of the chimney above the grid support at the be ginning of the burning is relatively low with heavy oils, such as between about 0.25 and 2.0 inches, and relatively high with lighter oils, such as between about 2.0 and 4.0 inches with a sample dish which is about 4 inches deep. The gas injected through the ring manifold burns in the shape of a conoidal flame ooaxially disposed within the chimney and above the sample dish. The oil vaporizing from the dish burns with a spherical flame which moves gradually about the oil surface below the gas flame. As the oil burns down, smoke may reappear and this may be eliminated either by increasing the gas rate to the ring manifold or lowering the chimney, or both.

This procedure continues until the oil flame is extinguished. The gas is then turned off, the chimney is raised, and the sample dish containing the coke residue is removed from the grid. It is placed in a kiln at 800 F. for about 20 minutes. Then the heat-loosened ash is transferred to a platinum crucible and calcined at 1000 F. for about 8.0 hours. It is weighed and calculated as weight percent of the oil sample. In this Way absolutely none of the oil is lost during the burning by occlusion with evolved soot and smoke but is completely oxidized in and from the sample dish leaving all nonvolatile and noncombustible materials deposited in the dish as an ash.

The degree of chimney adjustment during the burning varies somewhat depending upon the nature of the oil sample. With very heavy oils little, if any, adjustment is required and the chimney placed initially in a relatively low position can remain there without soot evolution. With lighter oils in which the chimney is originally placed in a relatively high position, some adjustment during the course of the burning is required ordinarily. With these light oils the chimney is gradually lowered and usually will be at or near the grid support at the end of the burning.

The structure of the apparatus provided for the method according to this invention will be more readily understood by reference to the attached drawing which shows an elevation view in partial cross section of the laboratory oil burner.

Referring now more particularly to the drawing, sample dish rests upon a transverse mesh or grid support 12 which is in turn supported through legs 14 on a bench top 16' or other support. Superimposed above the grid by means of stand 18, brackets 20 and 21, arms 22 and 23, and thumb screws 24 and 25 is chimney 26. This chimney is preferably cylindrical, fabricated of metal such as stainless steel sheet and open at its lower and upper ends 28 and 30 respectively. Disposed around the lower portion of chimney 26 is a row of openings 32. Extending around the inner surface of the chimney immediately below the open ngs 32 is ring manifold 34 which is also provided with a plurality of openings 36. This ring manifold may be tack welded or otherwise supported in the position shown. Inlet line 38 provided -with'flow control valve 40 opens through the wall of chimney 26 into the manifold. By means of gas valve 40 and thumb screws 24 and 25 or equavilent mechanical means, the adjustment of the chimney height and the gas rate may be individually or simultaneously controlled to maintain smoke free combustion within the chimney.

As an example of a laboratory apparatus constructed according to the foregoing description for the method of this invention, the following data are given. The sample dish was 6.75 inches maximum diameter and 3.3375 inches in height. Its nominal volume was 1000 milliliters. The heavy screen supported the sample dish between 4 and 6 inches from the bench. The chimney was constructed of type 304 stainless steel (18-8) 26 gauge sheet. The chimney was cylindrical, 8.25 inches inside diameter, and 16.0 inches high. The center line of the row of openings around the lower part of the chimney was 4.0 inches from the chimney bottom, the holes were 0.1875 inch. in diameter. Twenty-four of these holes were spaced around the periphery of the chimney uniformly 15 apart. The internal ring manifold consisted of a 0.125 inch diameter tubing provided with 12 holes 0.0625 inch. in diameter opening radially inward toward the vertical axis of the chimney.

The customary charge of oil to this apparatus is a Weighed sample approximately 750 milliliters in volume.

The apparatus performed perfectly in all cases without the formation of soot or smoke and gave for the first time reproducible results of duplicate samples. This is due to the fact that wet soot is at no time evolved from the system and all the ash in a uniformly taken sample remains to be weighed in the sample dish.

A particular embodiment of the present invention has been hereinabove describedin considerable detail by way of illustration. It should beunderstood that various other modifications and adaptations thereof may be made by those skilled in this particular art without departing from the spirit and scope of this invention as set forth in the appended claims.

I claim: 7

l. A method for burning oils which comprises burning the oil in a draft of air supplied at the bottom of a vertical burning zone, supplying additional air to said burning zone at a point above the burning oil, changing the relative position of the burning oil with respect to thelower open end of said burning zone to maintain smokeless burning of said oil, and introducing a controlled amount of additional fuel to said zone between the burning oil and the point of supply of said additional air.

2. A method according to claim 1 in combination with the step of controlling the rate of additional fuel flow so as to maintain smokeless burning of said oil.

3. An improved method for the burning of oil samples to determine the ash content thereof which comprises establishing a vertically elongated open ended burning zone, igniting an oil sample at a fixed position adjacent the bottom of said burning zone whereby air is drawn thereinto at the bottom, introducing fuel gas into said burning zone around the periphery thereof just above the burning oil, the draft so created in said burning zone causing the introduction thereinto of additional air around its. periphery just above the points of fuel gas injection, and moving said burning zone downwardly around the burning oil as the burning progresses and controlling the fuel gas flow rate into said burning zone to maintain smokeless burning.

4. A method according to claim 3 wherein said fuel gas flow rate is increased during the course of burning the oil in said burning zone to eliminate soot and smoke formation therein.

References Cited in the file of this patent UNITED STATES PATENTS 665,041 Tucker Jan. 1, 1901 1,322,453 Jungk Nov. 18, 1919 2,547,611 Young Apr. 3, 1951 FOREIGN PATENTS 24,923 Great Britain 1913 

1. A METHOD FOR BURNING OILS WHICH COMPRISES BURNING THE OIL IN A DRAFT OF AIR SUPPLIED AT THE BOTTOM OF A VERTICAL BURNING ZONE, SUPPLYING ADDITIONAL AIR TO SAID BURNING ZONE AT A POINT ABOVE THE BURNING OIL, CHANGEING THE RELATIVE POSITION OF THE BURNING OIL WITH RESPECT TO THE LOWER OPEN END OF SAID BURNING ZONE TO MAINTAIN SMOKELESS BURNING OF SAID OIL, AND INTRODUCING A CONTROLLED AMOUNT OF ADDITIONAL FUEL TO SAID ZONE BETWEEN THE BURNING OIL AND THE POINT OF SUPPLY OF SAID ADDITIONAL AIR. 